1. Field of the Disclosure
The present disclosure generally relates to a method of performing proximity discovery for a network entity and a user equipment (UE).
2. Description of Related Art
In the field of device to device (D2D) communication which is often referred to as a Proximity-based Services (ProSe) communication, a UE typically may discover another UE and subsequently performs D2D communication with another UE with or without the assistance of a core network such as an Evolved Packet Core (EPC). The aforementioned case such as discover another UE by using direct radio signal, without assistance of core network is called “direct discovery”. When a proximity discovery procedure occurs in direct discovery, an announcing UE and a monitoring UE may send discovery request to a network entity such as a ProSe function in the EPC network for announcing and monitoring the proximity discovery, respectively. The ProSe Function could be thought of as a collective logical function that implements network related actions required for ProSe. The ProSe Function may play different roles for each of the features of ProSe. Subsequently, the monitoring UE would check whether a match event occurred. An announcing UE could be a UE which announces certain information that could be used by a UE in proximity that has permission to discover. A monitoring UE could be a UE that monitors certain information of interest in proximities of announcing UEs.
There could be at least two kinds of ProSe direct discovery, namely an open discovery and a restricted discovery. The open discovery may predominate where there is no explicit permission that is needed from the UE being discovered, whereas the restricted discovery may only take place with explicit permissions from the UEs that are being discovered. For example, when a user wants to find his/her friends on a social network application, his/her device will likely perform the restricted discovery.
A direct discovery procedure may involve different types of discovery codes. A discovery filter of Discovery Response message may contain ProSe application code and ProSe application mask, and a ProSe application code of Discovery Response message or PC5 discovery message may contain ProSe application code. The ProSe application code may contain parameters not limited to public land mobile network (PLMN) ID of a ProSe function that assigned the ProSe application code and a temporary identity corresponding to the ProSe application ID name. The ProSe application code could be used by a monitoring UE for full or partial matching of PC5 Discovery messages received on PC5 interface. The ProSe application ID name could be used for identifying application related information for the ProSe-enabled UE. The ProSe application mask is a bitmask provided by the ProSe function in order to allow the monitoring UE to perform full or partial matching of PC5 Discovery messages received on the PC5 interface.
FIG. 1 shows a general call flow of a ProSe direct discovery procedure which is consistent with 3GPP TS 23.303 for example. In step S110, service authorization for ProSe direct services is performed for ProSe direct discovery. If the UE is authorized to announce, the UE would perform an announce request procedure (S130) to obtain a ProSe Application Code to be announced over the PC5 interface upon a request for announcing from upper layers. In step S131, when the UE is triggered to announce then it sends a discovery request for announcing to the ProSe Function in Home PLMN (HPLMN). In step S135, if the request is successful and is provided with ProSe Application Code then it starts announcing on PC5 interface. On the other hand, if the UE is authorised to monitor, the UE (such as an announcing UE) would perform a monitor request procedure (S150) to receive and process PC5_DISCOVERY messages upon a request for monitoring from upper layers. PC5_DISCOVERY message is transmitted from an announcing UE to a monitoring UE. In step S151, when the UE (such as a monitoring UE) is triggered to monitor, it sends a discovery request for monitoring to the ProSe Function. In step S155, if the request is successful and the UE is provided with a Discovery Filter consisting of ProSe Application Code(s) and/or ProSe Application Mask(s), the UE would start monitoring for these ProSe Application Codes on the PC5 interface. In step S170, when the monitoring UE detects that one or more ProSe Application Code(s) that match the discovery filter, the UE would send a match report including the ProSe Application Code(s) to the ProSe Function. There is a match event when, for any of the ProSe Application masks in a Discovery Filter, the output of a bitwise AND operation between the ProSe Application Code contained in the PC5_DISCOVERY message and this ProSe Application mask matches the output of a bitwise AND operation between the ProSe Application mask and the ProSe Application Code in the same discovery filter.
However, the aforementioned ProSe direct discovery procedure does not describe how the restricted discovery functions in detail as the discovery codes assigned for the restricted discovery is not described. The assignment of the discovery codes would be very important for the restricted discovery because only the target UEs that an announcing UE wants to discover would achieve the match event. Accordingly, there would be need to provide a method for assigning those discovery codes for the restricted discovery and a restricted discovery procedure.